Optical Transport Network (OTN) is defined inter alia in ITU-T G.709/Y.1331 (02/12) “Interfaces for the optical transport network,” the contents of which are incorporated by reference herein. As bandwidth rates have increased, e.g. 10 Gb/s to 40 Gb/s to 100 Gb/s and beyond, OTN related standards and addendums have been introduced to address these increased signal rates. For example, at the early onset of 40 Gb/s, the OTN standards and addendums at the time only specified an Optical channel Transport Unit level 3 (OTU3) signal without guidance on how to map/multiplex 4x independent G.Sup43 OTU2e/1e 10 Gb/s (i.e., 10 Gigabit Ethernet LAN PHY signals) into the 40 Gb/s OTU3 container. As expected, standards have some lag with vendor implementation, and vendors move forward with proprietary schemes to address higher rate signals before standardization is finalized. Once new, higher rate signals are standardized, there can be differences and rate variances with various vendors' proprietary schemes. Also, it is often important to keep rates consistent with various vendors' proprietary schemes to accommodate current optics and modems in optical systems.
For example, related to 40 Gb/s OTN, Ciena Corporation and Nortel MEN developed a proprietary OTU3+ scheme to overclock a 40 Gb/s OTN signal in order to fit Low Order (LO) Optical channel Data Unit level 2e (ODU2e) 10 Gb/s signals. The OTU3+ has a bit rate of approximately 43 Gb/s. Current standards define an OTU3e2 which has a bit rate slightly faster than the OTU3+. Thus, mapping an OTU3e2 onto optical equipment designed to support an OTU3+ involves mapping a slightly larger signal into a slightly smaller signal in OTN. Similarly, it is expected these same issues will arise when moving to 100 Gb/s, 1 Tb/s, etc. rate signals in OTN. Disadvantageously, there is no current mechanism within OTN to support mapping signals in such a fashion.
Specifically, the Asynchronous Mapping Procedure (AMP) and the Generic Mapping Procedure (GMP) schemes defined in G.709 do allow for mapping of slightly different rates, but these rates are generally within +/−100 parts per million (ppm). The aforementioned signals, while substantially similar in rate, have a difference in rate too great to use these schemes. Further, AMP and GMP do not work because these schemes only support mapping an Optical channel Data Unit level j (ODUj) into an Optical channel Payload Unit level k (OPUk) where the OPUk rate is greater than the ODUj rate. Again, the aforementioned signals have ODUk greater than the OPUk.